Conveyor oven with doors and sensors and mehod of operating same

ABSTRACT

A reliable conveyor oven minimizes escape of heat by minimizing the time that inlet and outlet openings appear in the baking oven. This may reduce energy consumption by 25%. The baking oven may have a conventional oven and an extension chamber, an outlet opening of the conventional oven acting as an inlet to the extension chamber, the extension chamber having an exit door, the baking oven also having an entrance door defining an entrance inlet. A conveyor holding food items runs through a length of the baking oven. An exit optical sensor may be attached to the extension chamber on opposite sides of the extension chamber such shat an item on the conveyor moving through the extension chamber interrupts a signal between the transmitted and the receiver. The exit sensor may be operatively engaged to a controller for actuating the exit door open and closed rotationally using a pneumatic piston.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to apparatuses and methods for conveyorovens, and, more particularly, to conveyor ovens with an extensionchamber and optical sensors sensing a product in the doorway andsignaling when the entrance and exit doors should rotate open, the doorsoperating independently.

For industrial applications servicing large numbers of food items,conveyor ovens are used instead of the conventional door oven. This hasthe additional advantage of not having to rely on the skill of theoperator as to how long to keep the food item, for example pizza, in theoven. The baking time is determined by the length of the chamber and thespeed of the conveyor.

Conventional conveyor ovens are widely used, among other things, forbaking, cooking, and heating (hereinafter referred to as “baking”) offood items such as pizza. The standard oven has an inlet opening and anoutlet opening and a conveyor on which the food items designated forbaking are placed. The loss of heat through the inlet and outletopenings is wasteful and leads to increased energy consumption. It alsocreates a hot and uncomfortable work environment that leads to anadditional waste of energy due to the need to air-condition the workenvironment.

There are approximately 100,000 conveyor ovens in the world in operation(Domino's® alone has 18,000 pizza ovens). The number one considerationin the purchase by a company of a conveyor oven nowadays is energyefficiency. It is well known that baking ovens lose heat when the fooditem passes through the oven since most conveyor oven sides are open forinlet and outlet. It is known in the prior art to try to solve thisproblem by using proximity sensors and a controller and a solenoid ormotor to operate baffle mechanisms that open and close to minimize heatloss. In U.S. Patent App. Publication no. U.S. 2005/0132899 to Huang,for example, a proximity sensor 40 is used to sense the approach of thefood item to the entrance door and the exit door is opened based on acalculation by the controller as to how long it will take the conveyorto carry the food item to the exit door, The controller controls asolenoid that actuates the baffle mechanism. This mechanism is notworkable for its intended purpose. It cannot sense food items on allsides of the conveyor; it cannot keep track effectively of amultiplicity of food items that enter the conveyor belt in shortintervals of time and space. The baffle mechanism is prone to gettingstuck. It is not believed to be a reliable means of achievingsignificantly reduced heat loss, energy consumption, unnecessary use ofair conditioning, worker discomfort, etc.

Another problem arising in these automated systems is that if the systemfails, the oven doors are stuck closed and the food in the oven burnsand is lost, which may be considered a catastrophe. It can also lead toa fire. Having to shut down the oven for a time until it is fixed causesfurther business losses.

There is a compelling need to have a conveyor oven and method thatsignificantly reduces heat loss and energy consumption from the oven andthat overcomes the drawbacks of the prior art. It would be particularlyhelpful if such an apparatus or method would prevent catastrophe, wouldmake the worker environment for industrial conveyor ovens more bearablein terms of temperature, and would save on use of air conditioning.

SUMMARY OF THE PRESENT INVENTION

One aspect of the present invention is a further aspect of the presentinvention is directed to a conveyor oven, comprising a baking ovenhaving an entrance door that rotates at a flexion region to an openposition thereby defining an inlet opening and having an exit door thatrotates at a flexion region to an open position; a conveyor traversingthe baking oven and the entrance and exit doors, the conveyor forholding items on a whole width of the conveyor; an entrance door opticalsensor for sensing items that contact a beam of light, the beam of lightcrossing a width of the conveyor upstream of the entrance door; an exitdoor optical sensor for sensing items that contact a beam of light, thebeam of light crossing a width of the conveyor upstream of the exitdoor; and a controller for receiving signals from the entrance sensorand from the exit sensor and for controlling when the entrance door andwhen the exit door are actuated

A further aspect of the present invention is a conveyor oven, comprisinga baking oven including a baking oven extension chamber at a downstreamend of the baking oven, the baking oven having an entrance door thatopens to an open position thereby defining an inlet opening and havingan exit door situated at an end of the baking oven extension chamber,the exit door opening to an open position; a conveyor traversing thebaking oven and the entrance and exit doors; an entrance door sensorupstream of the entrance door; an exit door sensor situated at thebaking oven extension chamber upstream of the exit door, the exit doorsensor sensing items on the conveyor as the items pass through thebaking oven extension chamber, the exit door and the entrance dooroperating independently of one another; a controller for receivingsignals from the entrance sensor and from the exit sensor and inresponse to these signals controlling when the entrance door and whenthe exit door are actuated, the controller programmed to actuate theentrance door and the exit door independently.

A still further aspect of the present invention is a method of operatinga conveyor oven, comprising (a) passing food items on a conveyor througha baking oven, the baking oven having a baking oven extension chamber;and (b) minimizing heat escaping from the baking oven by rotating anentrance door open whenever a food item crosses an entrance optical beamsituated upstream of the entrance door, rotating the entrance doorclosed after the food item enters the baking oven, rotating an exit doorat an exit end of the baking oven extension chamber open whenever thefood item crosses an exit optical beam in the baking oven extensionchamber, and rotating the exit door closed after the food item leavesthe baking oven extension chamber.

A yet still further aspect of the present invention is a conveyor oven,comprising a baking oven having a conventional oven and an extensionchamber, an outlet opening of the conventional oven acting as an inletto the extension chamber, the extension chamber having an exit door; aconveyor running through a length of the baking oven; an exit sensorincluding a transmitter and a receiver that are attached to theextension chamber on opposite sides of the extension chamber such thatan item on the conveyor moving through the extension chamber necessarilyinterrupts a signal between the transmitted and the receiver, the sensoroperatively engaged to a controller for actuating the exit door open andclosed.

A further aspect of the present invention is directed to a conveyor ovenkit for upgrading a conventional conveyor oven, comprising an extensionchamber structured to attached to an exit end of the conventionalstandard conveyor oven; an inlet door structured to attach to anentrance of the conventional convenyor oven; an inlet door sensor; anoutlet door structured to attach to an end of the extension chamber; anoutlet door sensor adapted to attach to the extension chamber; acontroller for controlling actuation of the pneumatic pistons; and twopneumatic pistons for actuating the inlet and outlet doors respectively.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, descriptions and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is a side view of a conveyor oven, in accordance with oneembodiment of the present invention;

FIG. 2 is a top plan view of a conveyor oven, in accordance with oneembodiment of the present invention;

FIG. 3A is an isometric view of a conveyor oven showing the exit doorpartially rotated open, in accordance with a further embodiment of thepresent invention;

FIG. 3B is an enlarged view of the circled area within FIG. 3A, inaccordance with a further embodiment of the present invention;

FIG. 4A is an isometric view of a conveyor oven showing the exit doorfully rotated open, in accordance with a further embodiment of thepresent invention;

FIG. 4B is an enlarged view of the circled area within FIG. 4A, inaccordance with a further embodiment of the present invention;

FIG. 5A is an isometric view of a conveyor oven showing the exit doorclosed, in accordance with a further embodiment of the presentinvention;

FIG. 5B is an enlarged view of the circled area within FIG. 5A, inaccordance with a further embodiment of the present invention;

FIG. 6A is an isometric view of a conveyor oven showing the entrancedoor closed, in accordance with a further embodiment of the presentinvention;

FIG. 6B is an enlarged view of the circled area within FIG. 6A, inaccordance with a further embodiment of the present invention;

FIG. 7A is an isometric view of a conveyor oven showing the entrancedoor partially open, in accordance with a further embodiment of thepresent invention;

FIG. 7B is an enlarged view of the circled area within FIG. 7A, inaccordance with a further embodiment of the present invention;

FIG. 8A is an isometric view of a conveyor oven showing the entrancedoor fully open, in accordance with a further embodiment of the presentinvention;

FIG. 8B is an enlarged view of the circled area within FIG. 8A, inaccordance with a further embodiment of the present invention;

FIG. 9 is an enlarged view similar to FIG. 5B except showing an exitdoor comprised of two separate half-doors, in accordance with a furtherembodiment of the present invention;

FIG. 10 is a flow chart showing a method in accordance with oneembodiment of the present invention;

FIG. 11 is a fragmentary isometric view of a mechanical shutter usableto open an exit door of the conveyor oven, in accordance with oneembodiment of the present invention; and

FIGS. 12A, 12B and 12C are plan views of an exit door illustratingsuccessive rotation open using a pivot arm, in accordance with oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplatedmodes of carrying out the invention. The description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention, since the scope of theinvention is best defined by the appended claims.

The present invention generally provides a conveyor oven for industrialbaking of food items, such as pizzas. The food items may be placed on aconveyor and may approach an entrance door optical sensor that may bejust outside the baking oven chamber and that may that signal acontroller to actuate a pneumatic piston which may cause the entrancedoor to rotate open axially. The baking oven has a baking oven extensionchamber. An exit door optical sensor may be situated just upstream ofthe exit door at the end of the extension chamber. Accordingly, a footitem inside the baking oven extension chamber may cross the light beamthat may run through the extension chamber whereupon the exit dooroptical sensor may (independently of the entrance door sensor) signalthe controller to actuate a second pneumatic piston which may cause theexit door to axially rotate open. The controller, after a delay, mayclose the entrance or exit door respectively. Energy consumption fromreduced heat loss may be reduced by at least 20%. The system may bedesigned to avoid catastrophe.

In contrast to prior art conveyor ovens, in which the conveor oveneither has no doors or has a baffle mechanism that is open and closedvertically with linear potion, the conveyor oven of the presentinvention may include an entrance door and an exit door that may rotateopen, thereby avoiding the problem of a baffle mechanism or verticalshutter whose linear motion makes it prone to getting stuck or jammed.In mechanical design, and more specifically regarding linear motion, thelength of the slider should be as long as possible and in practice (as arule of thumb) at least three times longer than the distance of theperpendicular to the motion direction vector of the sum of forces actingon the moving part, Otherwise, it may be prone to getting stuck. Theconveyor ovens may be eighty-five centimeters wide. The linear motionmay be seven centimeters since industrial conveyor ovens try to minimizeheat loss by only opening the amount necessary for the thickest fooditem to pass through it and have a standard outlet and inlet of sevencentimeters. In the prior art conveyor ovens, see, e.g. U.S. Patent App.Publication no. U.S. 2005/0132899 to Huang, a proximity sensor 40 may beused to sense the approach of the food item to the entrance door and theexit door is opened based on a calculation by the controller as to howlong it will take the conveyor to carry the food item to the exit door,Since the conveyor is typically 85 centimeters wide and since proximitysensors work within a range of 10-15 centimeters, one would need anextra sensitive proximity sensor that would generate false positivedetections of motion in order to detect pizzas on both sides of the oven(placing the food items on different sides is a common occurrence underthe pressure atmosphere of fast food preparation services). Use ofmultiple proximity sensors is either impractical or expensive. Incontrast, the conveyor oven of the present invention may use an opticalsensor comprising a transmitter and a receiver, with specially designedirises, whose light beam may traverse the entire width of the conveyorand thereby detect food items for the entire width of the oven'sconveyor belt. Moreover, the exit door may have its own optical sensorso that it is not opened based on when the entrance door is opened.Since it is common for many food items to be placed on the conveyor beltat short intervals from one another and hence pass through the entrancedoor at short time intervals, this makes it possible to keep track ofall these items simultaneously and program the controller to know whento actuate the entrance and exit doors for each item, something that itis impossible with proximity sensors. In further contrast to theconveyor ovens of the prior art, in which a simple baking oven isutilized, the present invention may utilize a baking oven that has abaking oven extension chamber. This makes it possible to have anindependent exit door sensor since placing the exit door sensor upstreamof the exit door puts the sensor in the oven where the intense heat ofthe oven would destroy it. The optical sensor may be attached to theextension chamber beyond the direct heat of the oven but its light beammay traverse the extension chamber upstream of the exit door. This mayfurther provide the advantage of being able to retrofit existingindustrial conveyor ovens with the apparatus of the present inventionsince drilling a hole in the thick wall of an existing oven to fastenthe optical sensor to the oven and keep it outside the heat near theexit door is impossible. Instead, the fastening may occur to the wall ofthe extension chamber which may be made thinner. This extension chambermay be attached to the end of the conventional industrial oven. In stillfurther contrast to prior art industrial conveyor ovens in which asolenoid or motor may be used to actuate the baffle mechanism (seeHuang), the present invention may utilize a pneumatic piston. Asolenoid, which operates based on magnetic force which decreasesinversely proportional to the square of the distance, and cannoteffectively control movement seven centimeters away, without thesolenoid being very expensive. A motor requires a gear and a driver,making it complex and unreliable without making it very expensive. Incontrast, the pneumatic piston used in the present invention can easilycover the 7 centimeter distance reliably and costs only $10 to $15. Infurther contrast to the prior art, in which conveyor ovens leak a largeamount of heat during operation, thereby wasting energy and renderingthe operator's working conditions very uncomfortable, the conveyor ovenof the present invention may reduce gas consumption by retaining theheat in the oven. Applicant tested a conveyor oven having the apparatusof the present invention for 25 days and by measuring the gas meterdaily, found a gas consumption reduction from 6.15 cubic meters down to4.62 cubic meters. Applicant tested the savings of liquid propane gas(lpg) daily consumption in two separate facilities using the conveyoroven of the present invention and recorded its reduction at 25% and 27%.The reduction in heat leakage from the oven also reduces use of airconditioning thereby further saving energy consumption. Furthermore,less carbon dioxide is emitted since there is less burning of gas neededto maintain the oven at 270 degrees Celsius. In still further contrastto the prior art, in which the danger of a failed apparatus may resultin a catastrophic situation in which the oven doors are shut, riskinginaccessibility and destruction of the food items and possible fire, theconveyor oven of the present invention may be more reliable in thatfailure of its pneumatic piston and/or optical sensors may not result inthe oven doors being shut; rather the doors would be left open in theevent of failure. This is because in some embodiments a spring may urgethe piston upward, resulting in the oven doors rotating open, and thepneumatic piston may counteract the force of the spring so as to onlyclose the doors as necessary (i.e. when a signal from the beams arereceived).

The principles and operation of a conveyor oven with doors and sensors,according to the present invention may be better understood withreference to the drawings and the accompanying description.

As seen from FIG. 1, and from FIGS. 6A, 6B, 7A, 7B, 8A, 8B which showthe entrance door in various positions, a conveyor oven 100 may comprisea baking oven 10 having an entrance door 31 (used interchangeably with“inlet opening door”) that may rotate axially at a flexion region 44such as a hinge or pivot to an open position thereby defining an inletopening 13. As seen from FIGS. 3A, 3B, 4A, 413, 5A, 513, conveyor oven100 may also have an exit door 41 (used interchangeably with “outletopening door”) that may rotate axially at a flexion region such as ahinge or pivot to an open position. Although exit door 41 may define anopening when it opens, exit door 41 may be positioned downstream of theoutlet opening 14 of baking oven 10, as explained further below. Ingeneral baking oven 10 is designed and constructed like existingconveyor ovens and the present invention refers to an upgrading of thestandard oven whereby it is equipped also with the doors and sensorssystem, as specified herein. Accordingly, the baking oven extensionchamber 17 may be added/retrofitted to an existing standard oven. Theinlet opening 13, the outlet opening 14 and the exit door 41 may bedesigned to allow passage of food items seven centimeters high. In orderembodiments, they may allow passage of items ten centimeters high.

As shown in FIGS. 1-2, the inlet door 31 may cover the inlet opening 13down to slightly above the top surface of the conveyor 12 in a way thatenables the conveyor 12 to move into the interior of the oven 10 evenwhen the inlet door 31 is closed. The inlet door 31 may have the generalshape of a flat plate and its size may correspond to that of the inletopening 13. The inlet door 31 may open and close on an axial hinge 323such that when the inlet door 31 opens, it opens inward, into theinterior of the oven 10. The same is true for the outlet door 41 whichalso may have an axial hinge 423 but may open from the interior of theoven 10 outward.

Conveyor oven 100 may include a conveyor 12 that may traverse the bakingoven 10 and the entrance and exit doors 31, 41. Conveyor 12 may holdfood items and may be able to do so at any portion of the width of theconveyor belt.

As shown in FIG. 1 and in FIGS. 6A, 6B, 7A, 7B, 8A, 8B, conveyor oven100 may also include an entrance door sensor 32, which may be anentrance door optical sensor 32, for sensing food items that contact thebeam of light of sensor 32. The beam of light may cross the width of theconveyor upstream of the entrance door and may be located near entrancedoor 31, such as within ten centimeters of the entrance door 31.

As seen in FIG. 1 and in FIGS. 3A, 3B, 4A, 4B, 5A, 513, conveyor oven100 may also include an exit door optical sensor 42 for sensing fooditems that contact the exit door optical sensor's 42 beam of light, thebeam of light crossing a width of the conveyor upstream of the exit doorand located near exit door 41, such as within ten centimeters of theexit door. Baking oven 10 may include a baking oven extension chamber 17in open communication with the inside of the conventional ovenrepresenting the remaining portion of baking oven 10. Accordingly, asseen in FIG. 2 components 422, 421 of exit door sensor 42 may besituated at the baking oven extension chamber 17 upstream of the exitdoor 41, While the actual components of exit door sensor 42 may beattached to extension 17 on the outside of the baking oven extensionchamber 17, the optical beam (not shown) or other interruptable signalbetween the sensor components 422, 421 may pass through the baking ovenextension chamber 17 from one side of its width to the other.Accordingly, exit door sensor 42 may sense items, such as food items, onthe conveyor 12 as these food items pass through the baking ovenextension chamber 17. Consequently, the exit door 41 and the entrancedoor 31 may operate independently of one another and similarly, theentrance door sensor 32 and the exit door sensor 42 may operateindependently of one another. The controller 15 need not base actuationof the exit door 41 on when the entrance door 31 was actuated or whenthe inlet sensor 32 sent a signal that a food item passed it.

The sensor 42 of the outlet door 41 may be positioned outside the oven10 at a slight distance from the outlet opening 14 so that sensor 42 isnot be within the interior of the oven where the temperature isespecially high, which would prevent use of a common, standard sensor.The outlet door 42 may, therefore, be positioned outside the baking ovenextension chamber 17, which is an extension chamber added to theconventional oven 11 of baking oven 10 to prevent loss of heat from theinterior of the oven 10 through the gap between the outlet opening 14and the outlet door 41 and also to support the outlet opening door 41.The extension chamber 17 may be made of a top plate and two side plates.The side plates of the extension chamber 17 may be and should be made ofa material that will enable the sensor 42 to function, and in case of anoptical sensor 42, the said plates should be made of a transparentmaterial, such as glass. It is also possible that a hole be located ineach of the said plates to enable passage of the said light beam. Afterthe item exits the interior of the conventional oven 11 of baking oven10 through the outlet opening 14, it may enter the extension chamber 17where the sensor 42 detects its presence and sends an appropriate signalthat causes the outlet door 41 to open, for example by rotating axially,just before the item reaches the door 41.

As seen in FIGS. 1-2, conveyor oven 100 may also include a controller 15for receiving signals from the entrance door sensor 32 and from the exitdoor sensor 42 and for controlling when the entrance door 31 and whenthe exit door 41 are actuated. More directly, the controller 15 maycontrol actuation of at least one pneumatic piston 16 operativelyengaged to entrance door 31 and at least one pneumatic piston 16operatively engaged to exit door 41 so that actuation or de-actuation ofthe piston may close or open the exit, entrance door 41, 31.

The pneumatic piston 16 (which may be based on air or may be a hydraulicpiston) may be attached to oven 10 by means of bracket 62 (see FIG. 1),may be attached or operatively engaged to the doors 31, 41, for exampleby means of an arm 61 and may open and close the doors 31, 41 followingcommands that it receives from the controller 15. As noted, entrance andexit doors 31, 41 may rotate at a flexion region 44. As shown in FIG.12A, instead of the flexion region 44 comprising a hinge 323, 423, asshown in FIG. 2, flexion region 44 may comprise a pivot arm 69 that maymove so as to guide exit door 41 or entrance door 31 along an arcedtrack (not shown) or guide that is not a sharp curve so that doors 31,41 move primarily vertically but also partially horizontally. Thisavoids having the doors 31, 41 move in linear motion so as to avoid theproblems, such as getting stuck, associated with such linear motion.FIG. 12B shows the pivot arms 69 having rotated to open the exit door 41partially and FIG. 12C shows a view similar to FIG. 12B but after fullrotation of pivot arms 69 so that exit door is now open.

However, in order to prevent a catastrophic situation if either thepneumatic piston or the optical sensor fails and the oven doors remainshut, the apparatus may be designed to default to an “open oven”situation whenever either or both of the optical sensors 32, 42 andpneumatic pistons 16 fail to operate. For example, the pneumatic piston16 close at least one of the entrance door and the exit door by opposinga force of a spring such that if the pneumatic piston fails the at leastone of the entrance door and the exit door remain open, thereby avertingcatastrophic consequences of a closed baking oven that cannot be opened.Spring 19 may urge the pneumatic piston up so as to maintain the atleast one of the entrance door and the exit door open until thepneumatic piston is actuated to counteract force of the spring by movingdownward.

Sensors 32, 42 may be capable of detecting items on the conveyor andsending a signal accordingly. Preferably, sensors 32, 42 are opticalsensors composed of a transmitter 321, 421 and a receiver 322, 422located on either side of the conveyor upstream of and close to theinlet opening 13 or outlet door 41, respectively. Note that outlet orexit sensor 42 may be slightly downstream of outlet or exit opening 17Aof the conventional oven 11 yet upstream of exit door 41 and of theoutlet opening 14 of extension chamber 17/baking oven 10. An opticalbeam or other interruptable signal may run between the two parts of thesensor 32, 42 such that when there is an item on the conveyor designatedto be baked in the oven, the sensor 32, 42 sends a signal to thecontroller 15 which in turn sends an appropriate signal to the pneumaticpiston 16 to open the inlet door 31 or the outlet 41 door. When thesensor 32, 42 detects that the item has passed and that there are noadditional items on the conveyor, a signal is sent to the controller 15which may send a signal to the actuator, which may be a pneumatic piston16 to close the appropriate door 31, 41. This signal may be sent after ashort delay (holding time) in order to prevent repeated opening andclosing of the door 31, 41 when items are located on the conveyor atsmall intervals and also so to prevent the door from closing on the itemitself.

This may prevent the sensors could cause the doors to open and close atan inefficient and rapid pace when there are items on the conveyor thatare designated to be warmed and baked in the interior of the oven anditems are positioned on the conveyer at small intervals. Instead, thedelay action may cause the doors to close only when the user indeedstops placing items on the conveyor for a certain period of time. Theholding time is intended to prevent the door from hitting the item uponclosing, since the beam between the sensors is located in parallel andat a certain distance from the door line. In other words, when the itempasses through the beam's line it is still located opposite and underthe door line for a certain period of time. The holding time iscontrolled by programming the controller and is adjusted according tothe conveyor's speed, the speed at which the door closes, and thedimensions of the items and the door.

As seen in FIG. 1, baking oven 10 may also be equipped with a visual oraudio warning device 18 that indicates to the oven operator that theoutlet door 41 has closed and that the food item exiting the baking oven10 is ready for collection.

Regarding the entrance and exit doors, the terms “operatingindependently” and “independently timed” refer to the fact that the exitdoor does not operate in a manner dependent on the timing of theoperation of the entrance door or of the entrance door sensor.

The present invention may also be described as a conveyor oven 100comprising a baking oven 10 that includes a conventional oven 11 and anextension chamber 17. An outlet opening 17A of the conventional oven mayact as an inlet to the extension chamber 17. Extension chamber may havean exit door 41. A conveyor 12 may run through the length of the bakingoven 10. An exit sensor 42 may include a transmitter 421 and a receiver422 that are attached to the extension chamber 17 on opposite sides ofthe extension chamber 17 such that an item on the conveyor 12 movingthrough the extension chamber 17 necessarily interrupts a signal, suchas a light beam positioned within a centimeter up from the conveyor 12,between the transmitted 421 and the receiver 422. The sensor 42 may beoperatively engaged to a controller 15 that may actuate the exit door 41open and closed, for example by actuating a pneumatic piston 16 thaturges the exit door 41 to rotate to a closed position against the forceof a spring that urges the exit door 41 open. Exit door 41 may open andclose by rotating axially. Baking oven 10 may further comprise anentrance door 31 structured to rotate to an open position and therebydefine an inlet opening 13 when an item on the conveyor nears theentrance door 31 and interrupts a signal of an entrance sensor 32 thatmay be situated upstream of the entrance door 31.

Controller 15 may receiving signals from the entrance sensor and fromthe exit sensor and controller 15 may also receive a signal when theexit door is closed. Accordingly, a warning device that is selected froma visual warning device and an audio warning device may be operativelyengaged to the controller so as to receive a signal to be actuated whenthe exit door has closed.

As seen from FIG. 9, the present invention may be described as a method100 of operating a conveyor oven. Method 100 may have a step 110 ofpassing food items on a conveyor through a baking oven, the baking ovenhaving a baking oven extension chamber. Method 100 may also have afurther step 120 of minimizing heat escaping from the baking oven by (a)rotating an entrance door open whenever a food item crosses an entranceoptical beam situated upstream of the entrance door, (b) rotating theentrance door closed after the food item enters the baking oven, (c)rotating an exit door at an exit end of the baking oven extensionchamber open whenever the food item crosses an exit optical beam in thebaking oven extension chamber, and (d) rotating the exit door closedafter the food item leaves the baking oven extension chamber.

In some versions, method 100 may further comprise using a controllercontrolling actuation of an at least one pneumatic piston, the at leastone pneumatic piston operatively engaged to the at least one of theentrance door and the exit door, in order to rotate the exit andentrance doors open and closed. Method 100 may in some versions alsocomprise, for at least one of the entrance door and the exit door,mechanically urging a pneumatic piston engaged to the at least one ofthe entrance door and exit door up so as to maintain the at least one ofthe entrance door and exit door open unless at least one of the entranceoptical beam and the exit optical beam signals a controller to actuatethe pneumatic piston downward.

As seen in FIG. 1, a further embodiment of the present invention, aconveyor oven retrofit or installation kit 101 for upgrading aconventional conveyor oven 11 may contain an inlet door 31, an inletdoor sensor 32, an outlet door 41, an outlet door sensor 42, acontroller 15, a pneumatic piston 16, an extension chamber 17 that canbe installed on existing, standard conveyor ovens 11. The kit 10 mayalso contain a warning device 18.

As seen in FIG. 10, in certain preferred embodiments, the advantages ofthe present invention may be further enhanced by constructing exit door41 such that exit door 41 is comprised of two half-doors, a firsthalf-door and a second half-door. In this way, and since pizza andcertain other food may be narrower than half the width of the conveyoroven, which may be 85 centimeters wide, only one half-door comprisingone half of the width of the exit door 41 need open in most cases. Thesame may be done for entrance door 31 which may be comprised of twohalf-doors (not shown) whereby one half-door of entrance door 31 opensand the other half remains closed when food items narrower than half thewidth of the oven pass through. Whether for exit door 41 or entrancedoor 31, one piston 16 of the at least one pneumatic piston 16 may besituated on one side of the oven so as to be connected to one of thehalf-doors and a second piston 16 of the at least one piston may besituated on the other side of the oven so as to be connected to theother one of the half-doors.

In some preferred embodiments, as seen in FIG. 3B, FIG. 4B and FIG. 5B,oven 10 may also comprise an actuator 93 for manually opening the exitdoor 41 in order to manually re-insert a food item in order to bake thefood item further (i.e. to make them “well-done”). In the entrance, ifthe user needs to open the entrance door 31 manually all the user needsto do is to manually cause interference to the beam of light thusblocking the beam, and the entrance door 31 will be opened immediately.The entrance door 31 will not shut for the set period of time which isthe time required for a food item to clear the doorway. This is not thecase for the exit. If the user needs to open the exit door 41 manuallyby manually interfering with the beam of light in order to return apizza into the oven for extra backing to make it well done, the usercannot do so because the beam may be behind the exit door 41 and theexit door is shut. Accordingly, as shown in FIG. 11, oven 10 may alsocomprise a special mechanical shutter 99 that may be actuated byactuator 93 and that is able to obstruct the optical beam. Mechanicalshutter 99 may be situated at the side of the oven 10. In one version,the user needs to push on this actuator in order to cause the shutter 99to block the optical beam 444 (shown schematically in FIG. 11) of thesensor comprising the transmitter 421 and receiver 422 and thereby openthe exit door 41 even when no food item is on the conveyor. Shutter 99may be capable, in an actuated mode, of interrupting the beam of light444 crossing a width of the conveyor 10 upstream of the exit door 41.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made.Therefore, the claimed invention as recited in the claims that follow isnot limited to the embodiments described herein.

What is claimed is:
 1. A conveyor oven for baking food items,comprising: a baking oven including a baking oven extension chamber at adownstream end of the baking oven, the baking oven having an entrancedoor that rotates at a hinge to an open position thereby defining aninlet opening and having an exit door that is situated at a downstreamend of the baking oven extension chamber and that rotates at a hinge toan open position; a conveyor traversing the baking oven and the entranceand exit doors, the conveyor for holding food items on a whole width ofthe conveyor; an entrance door optical sensor for sensing food itemsthat contact a beam of light, the beam of light crossing a width of theconveyor upstream of the entrance door; an exit door optical sensor forsensing items that contact a beam of light, the beam of light crossing awidth of the conveyor upstream of the exit door; and a controller forreceiving signals from the entrance sensor and from the exit sensor andin response to these signals controlling when the entrance door and whenthe exit door are actuated, the controller programmed to actuate theentrance door and the exit door independently of one another.
 2. Theconveyor oven of claim 1, wherein the light beam of the exit dooroptical sensor is situated in a baking oven extension chamber.
 3. Theconveyor oven of claim 1, wherein the entrance door rotates open axiallyand the exit door rotates open axially.
 4. The conveyor oven of claim 1,wherein at least one of the exit door and the entrance door is comprisedof a first and a second half-door.
 5. The conveyor oven of claim 1,wherein a pivot arm pivots to rotate the exit door open and closed. 6.The conveyor oven of claim 1, further comprising a shutter configured,in an actuated mode, to block the full beam of light crossing a width ofthe conveyor upstream of the exit door so as to trigger an opening ofthe exit door even when no item held on the conveyor contacts the beamof light upstream of the exit door.
 7. A conveyor oven for baking fooditems, comprising: a baking oven including a main oven and a baking ovenextension chamber the baking oven extension chamber at a downstream endof the baking oven, the baking oven having an entrance door that rotatesat a first flexion region to an opens position inwardly into theinterior of the main oven thereby defining an inlet opening and havingan exit door situated at a downstream end of the baking oven extensionchamber thereby defining an outlet opening, the exit door rotating openat a second flexion region outwardly in a direction away from theinterior of the main oven to an open position, the inlet openingdefining a plane on which the first flexion region at least partiallylies, the outlet opening defining a plane on which the second flexionregion at least partially lies, a conveyor traversing the baking ovenand the entrance and exit doors; an entrance door sensor upstream of theentrance door; an exit door sensor situated at the baking oven extensionchamber upstream of the exit door, the exit door sensor sensing items onthe conveyor as the items pass through the baking oven extensionchamber, the exit door and the entrance door operating independently ofone another; a controller for receiving signals from the entrance sensorand from the exit sensor and in response to these signals controllingwhen the entrance door and when the exit door are actuated, thecontroller programmed to actuate the entrance door and the exit doorindependently.
 8. The conveyor oven of claim 7, wherein an optical beamof the exit door sensor crosses a width of the baking oven extensionchamber inside the baking oven extension chamber and wherein food itemscontacting the optical beam trigger rotation of the exit door to theopen position.
 9. The conveyor oven of claim 7, wherein the baking ovenextension chamber is open to an inside of a remainder of the bakingoven.
 10. The conveyor oven of claim 7, wherein the baking ovenextension chamber can be added/retrofitted to existing baking ovens. 11.The conveyor oven of claim 7, wherein the entrance door opens byrotating and wherein the exit door opens by rotating, and wherein thecontroller is programmed to open at least one of the entrance door andexit door rotates by default whenever at least one of the followingfails to operate: (i) an actuator of the entrance door or of the exitdoor, (ii) the exit door sensor or the entrance door sensor.
 12. Theconveyor oven of claim 7, wherein at least one of the entrance door andthe exit door are actuated by a pneumatic piston controlled by thecontroller.
 13. The conveyor oven of claim 12, wherein the pneumaticpiston closes the at least one of the entrance door and the exit door byopposing a force of a spring such that if the pneumatic piston fails theat least one of the entrance door and the exit door remain open, therebyaverting catastrophic consequences of a closed baking oven that cannotbe opened.
 14. The conveyor oven of claim 13, wherein a spring urges thepneumatic piston up so as to maintain the at least one of the entrancedoor and the exit door open.
 15. A method of operating a conveyor ovenfor baking food items, the method comprising: (a) passing food items ona conveyor through a baking oven, the baking oven having a main oven anda baking oven extension chamber; and (b) minimizing heat escaping fromthe baking oven by rotating an entrance door open on a first flexionregion to an open position inwardly into the interior of the main ovento define an inlet opening, the inlet opening defining a plane on whichthe first flexion region at least partially lies, whenever a food itemcrosses an entrance optical beam situated upstream of the entrance door,the entrance optical beam generated by an entrance door sensor, rotatingthe entrance door closed after the food item enters the baking oven, theentrance door in a closed position not situated in the main oven,rotating an exit door at an exit end of the baking oven extensionchamber outwardly away from the interior of the oven at a second flexionregion to an open position to define an outlet opening whenever the fooditem crosses an exit optical beam in the baking oven extension chamber,the exit optical beam generated by an exit door sensor, the outletopening defining a plane on which the second flexion region at leastpartially lies, rotating the exit door closed after the food item leavesthe baking oven extension chamber, and urging at least one of theentrance door and exit door to an open position so that the at least oneof the entrance door and exit door defaults to said open positionwhenever at least one of the following fails to operate: (i) an actuatorof the entrance door or of the exit door, (ii) the exit door sensor orthe entrance door sensor.
 16. The method of claim 15, further comprisingusing a controller controlling actuation of an at least one pneumaticpiston, the at least one pneumatic piston operatively engaged to the atleast one of the entrance door and the exit door, in order to rotate theexit and entrance doors open and closed.
 17. The method of claim 15,further comprising, for at least one of the entrance door and the exitdoor, mechanically urging a pneumatic piston engaged to the at least oneof the entrance door and exit door up so as to maintain the at least oneof the entrance door and exit door open unless at least one of theentrance optical beam and the exit optical beam signals a controller toactuate the pneumatic piston downward.
 18. A conveyor oven kit forupgrading a conventional conveyor oven for pizza, comprising: anextension chamber structured to be attached to an exit end of theconventional conveyor oven; an inlet door structured to attach to anentrance of the conventional convenyor oven; an inlet door sensor; anoutlet door structured to attach to an end of the extension chamber; anoutlet door sensor adapted to attach to the extension chamber; twopneumatic pistons for actuating the inlet and outlet doors respectively;and a controller for controlling actuation of the pneumatic pistons. 19.The method of claim 15, further comprising configuring the entrance andexit doors to open by default whenever at least one of the followingfails to operate: (i) an actuator of the entrance door or of the exitdoor, (ii) the exit door sensor or the entrance door sensor.
 20. Theconveyor oven for baking food items of claim 7, wherein the entrancedoor lies on the plane defined by the inlet opening when the entrancedoor is in a closed position and wherein the exit door lies on the planedefined by the outlet opening when the exit door is in the closedposition.